Martins-Green M, Tilley C, Schwarz R, Hatier C, Bissell M J
Division of Cell and Molecular Biology, Lawrence Berkeley Laboratory, Berkeley, California 94720.
Cell Regul. 1991 Sep;2(9):739-52. doi: 10.1091/mbc.2.9.739.
The gro genes encode for secreted proteins with sequence homologies to inflammatory mediators. Little is known about the function of these proteins or their regulation. The chicken gro (9E3/CEF4) is expressed abundantly in the cells of proliferating cultures but at very low levels in confluent cultures. In vivo, this gene is expressed in connective tissue and overexpressed at sites of injury, especially in areas of neovascularization. Here we provide a bridge between these observations by examining in culture the effect on 9E3 expression and DNA synthesis induced by cell damage and by addition of factors known to be released on wounding. We mimicked wounding by scraping swaths across confluent cultures of embryonic fibroblasts and determined the time dependence of expression of 9E3 mRNA and incorporation of 3H-thymidine. We find that 9E3 is (1) transiently expressed after "wounding" or serum-stimulation; (2) expressed in a cell cycle phase-dependent manner; it is triggered during the G0-G1 transition or early in G1 and subsides during S-phase; and (3) stimulated to high levels by a-fibroblast growth factor (aFGF), bFGF, transforming growth factor alpha (TGF alpha), and TGF beta, to intermediate levels by platelet-derived growth factor and not stimulated by epidermal growth factor. We also find that cells that are constantly cycling do not express 9E3, indicating that they skip either the portion of the cell cycle where 9E3 is induced or that they constitutively express a repressor of transcription or an RNA-degrading enzyme. Taken together, these observations suggest that the product of this gene could play more than one role in vivo. For example, in normal tissues the 9E3 protein could be involved in the exit of cells from the resting stage, whereas during wound healing the secreted protein or its cleavage products also could play a role in angiogenesis.
gro基因编码的分泌蛋白与炎症介质具有序列同源性。关于这些蛋白质的功能及其调控知之甚少。鸡gro（9E3/CEF4）在增殖培养的细胞中大量表达，但在汇合培养的细胞中表达水平极低。在体内，该基因在结缔组织中表达，并在损伤部位过度表达，尤其是在新血管形成的区域。在这里，我们通过在培养中研究细胞损伤以及添加已知在伤口处释放的因子对9E3表达和DNA合成的影响，为这些观察结果搭建了一座桥梁。我们通过刮擦汇合的胚胎成纤维细胞培养物来模拟损伤，并确定9E3 mRNA表达的时间依赖性以及3H-胸苷的掺入情况。我们发现9E3：（1）在“损伤”或血清刺激后短暂表达；（2）以细胞周期阶段依赖性方式表达，在G0-G1期转换期间或G1期早期被触发，并在S期减弱；（3）被α-成纤维细胞生长因子（aFGF）、碱性成纤维细胞生长因子（bFGF）、转化生长因子α（TGFα）和转化生长因子β（TGFβ）刺激至高水平，被血小板衍生生长因子刺激至中等水平，而不被表皮生长因子刺激。我们还发现持续循环的细胞不表达9E3，这表明它们要么跳过了诱导9E3的细胞周期部分，要么持续表达转录抑制因子或RNA降解酶。综上所述，这些观察结果表明该基因的产物在体内可能发挥多种作用。例如，在正常组织中，9E3蛋白可能参与细胞从静止期退出，而在伤口愈合过程中，分泌的蛋白质或其裂解产物也可能在血管生成中发挥作用。
